Excerpts from Fabiano Rosas's message of February 14, 2022 11:13 pm: > Nicholas Piggin <npig...@gmail.com> writes: > >> Use KVM_CAP_PPC_AIL_MODE_3 to determine cap-ail-mode-3 support for KVM >> guests. Keep the fallback heuristic for KVM hosts that pre-date this >> CAP. >> >> This is only proposed the KVM CAP has not yet been allocated. I will >> ask to merge the new KVM cap when there are no objections on the QEMU >> side. >> >> not-yet-Signed-off-by: Nicholas Piggin <npig...@gmail.com> >> --- >> hw/ppc/spapr_caps.c | 2 +- >> linux-headers/linux/kvm.h | 1 + >> target/ppc/kvm.c | 18 +++++++++++++++++- >> target/ppc/kvm_ppc.h | 4 ++-- >> 4 files changed, 21 insertions(+), 4 deletions(-) >> >> diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c >> index 5fd4a53c33..5cc80776d0 100644 >> --- a/hw/ppc/spapr_caps.c >> +++ b/hw/ppc/spapr_caps.c >> @@ -619,7 +619,7 @@ static void cap_ail_mode_3_apply(SpaprMachineState >> *spapr, >> ERRP_GUARD(); >> >> if (kvm_enabled()) { >> - if (!kvmppc_supports_ail_3()) { >> + if (!kvmppc_has_cap_ail_3()) { >> error_setg(errp, "KVM implementation does not support >> cap-ail-mode-3"); >> error_append_hint(errp, "Try appending -machine >> cap-ail-mode-3=off\n"); >> return; >> diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h >> index 02c5e7b7bb..d91f578200 100644 >> --- a/linux-headers/linux/kvm.h >> +++ b/linux-headers/linux/kvm.h >> @@ -1130,6 +1130,7 @@ struct kvm_ppc_resize_hpt { >> #define KVM_CAP_BINARY_STATS_FD 203 >> #define KVM_CAP_EXIT_ON_EMULATION_FAILURE 204 >> #define KVM_CAP_ARM_MTE 205 >> +#define KVM_CAP_PPC_AIL_MODE_3 210 >> >> #ifdef KVM_CAP_IRQ_ROUTING >> >> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c >> index 128bc530d4..d0d0bdaac4 100644 >> --- a/target/ppc/kvm.c >> +++ b/target/ppc/kvm.c >> @@ -90,6 +90,7 @@ static int cap_ppc_nested_kvm_hv; >> static int cap_large_decr; >> static int cap_fwnmi; >> static int cap_rpt_invalidate; >> +static int cap_ail_mode_3; >> >> static uint32_t debug_inst_opcode; >> >> @@ -154,6 +155,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s) >> } >> >> cap_rpt_invalidate = kvm_vm_check_extension(s, >> KVM_CAP_PPC_RPT_INVALIDATE); >> + cap_ail_mode_3 = kvm_vm_check_extension(s, KVM_CAP_PPC_AIL_MODE_3); >> kvm_ppc_register_host_cpu_type(); >> >> return 0; >> @@ -2563,10 +2565,24 @@ int kvmppc_has_cap_rpt_invalidate(void) >> return cap_rpt_invalidate; >> } >> >> -int kvmppc_supports_ail_3(void) >> +int kvmppc_has_cap_ail_3(void) >> { >> PowerPCCPUClass *pcc = kvm_ppc_get_host_cpu_class(); >> >> + if (cap_ail_mode_3) { >> + return 1; >> + } >> + >> + if (kvm_ioctl(kvm_state, KVM_CHECK_EXTENSION, KVM_CAP_PPC_AIL_MODE_3) >> == 0) { >> + return 0; >> + } > > This is not needed here it seems.
This is to test whether the capability is recognised by the HV. kvm_vm_check_extension() treats ioctl error as 0 capability but we want to do this extra heuristic. I'm not sure if there's a better standard way to do this. Thanks, Nick